An industrial fabric or belt is an endless structure in the form of a continuous loop such as a forming fabric, press fabric, dryer fabric or process belt (e.g., shoe press belt, transfer belt, calendar belt), reel belt, a structure used as an impression fabric, through air dryer (“TAD”) fabric used in the production of tissue and towel (together known as “paper machine clothing” or “PMC”). Other industrial fabrics include: corrugator belts for producing corrugated boxboard, fabrics and belts and sleeves used in the production of nonwovens by processes such as melt-blowing, spun bond, hydroentangling, or air laid; a fabric used in a sludge filter or other wet filtration processes; or a fabric used in textile finishing processes such as sanforizing; belts used in hide tanning; and other conveyor belts such as those used in food processing.
While the discussion here is for the papermaking process in general, the application of the present disclosure is not considered limited thereto.
During the papermaking process, a cellulosic fibrous web is formed by depositing a fibrous slurry, that is, an aqueous dispersion of cellulose fibers, onto a moving forming fabric in a forming section of a paper machine A large amount of water is drained from the slurry through the forming fabric, leaving the cellulosic fibrous web on the surface of the forming fabric.
The newly formed cellulosic fibrous web proceeds from the forming section to a press section, which includes a series of press nips. The cellulosic fibrous web passes through the press nips supported by a press fabric, or, as is often the case, between two such press fabrics. In the press nips, the cellulosic fibrous web is subjected to compressive forces which squeeze water therefrom, and which adhere the cellulosic fibers in the web to one another to turn the cellulosic fibrous web into a paper sheet. The water is accepted by the press fabric or fabrics and, ideally, does not return to the paper sheet.
The paper sheet finally proceeds to a dryer section, which includes at least one series of rotatable dryer drums or cylinders, which are internally heated by steam. The newly formed paper sheet is directed in a serpentine path sequentially around each in the series of drums by a dryer fabric, which holds the paper sheet closely against the surfaces of the drums. The heated drums reduce the remaining water content of the paper sheet to a desirable level through evaporation.
It should be appreciated that the forming, press and dryer fabrics all take the form of endless loops on the paper machine and function in the manner of conveyors. It should further be appreciated that paper manufacture is a continuous process which proceeds at considerable speeds. That is to say, the fibrous slurry is continuously deposited onto the forming fabric in the forming section, while a newly manufactured paper sheet is continuously wound onto rolls after it exits from the dryer section.
In the production of tissue or towel, forming and press fabrics provide the same function as in paper making above. There may also be other fabrics such as impression fabrics or TAD fabrics, as well as reel belts.
Base fabrics, which form an important portion of the above discussed fabrics, take many different forms. For example, they may be woven either endlessly or flat woven and subsequently rendered into endless form with a woven seam using one or more layers of machine direction (“MD”) and cross-machine direction (“CD”) yams. Further, the woven base fabrics may be laminated by placing one base fabric within the endless loop formed by another, and joining or laminating together by various means known to those skilled in the art such as by needling a staple fiber batt through both base fabrics to join them to one another.
Different polymeric materials may be used in the formation of MD/CD yarns and if present, the batt fibers that form these fabrics. One example of a polymeric resin that may be used for this purpose is polyester. Because these fabrics are exposed to harsh environments, it is essential that the material used to form these yams and fibers exhibit good abrasion-resistant properties. While pure (100%) material used for a yarn or fiber, for example, polyester as a forming fabric yarn, has excellent required yam modulus, it has relatively poor abrasion resistance. While attempts to improve these shortcomings have been made, none have shown the required level of improvement.
Other structural components such as foils or films, can be used as a layer in a structure for the uses aforementioned. Such films comprise polymers such as, but not limited to, polyester or polyurethane.
Lastly, coatings such as used to manufacture shoe press belts, calendar belts, transfer belts, certain tissue/towel impression fabrics, and several of the engineered fabrics also have this requirement of anti-contamination or easier removal of contaminants The coatings may comprise polyurethane or other polymers.
Products comprising various amounts of inorganic compounds and/or mineral fillers have been known. For example, U.S. Pat. No. 6,323,271 pertains to a polyester resin containing silica beads used in beverage containers to reduce the surface coefficient of friction. U.S. Pat. Nos. 5,278,221, 5,278,205, 5,137,939, and 5,132,356 likewise pertain to films of polyester containing glass spheres to reduce the dynamic coefficient of friction of the film and the addition of fumed silica to improve the static coefficient of friction of the film. U.S. Pat. No. 3,230,184 relates to a PET resin for molding with a fibrous material and hollow discrete spheres of silicate-based glass. Further, European Pat. No. EP648,802 relates to polyester film with polyester polymer containing precipitated silica particles and calcined clay. British Pat. No. GB954024A discloses the production of improved polyester filaments with some form of silica particles less than 20 microns in diameter. U.S. Pat. No. 3,486,266 appears to disclose a sheath core material with plasticized polyvinyl chloride having microscopic glass beads dispersed therein. U.S. Pat. No. 5,207,959 discloses fumed silica with a particle size of between 5 and 15 nm mixed into a molten polymer. Further, U.S. Pat. No. 5,132,356 relates to a polyester film containing small glass spheres and fumed silica. In that disclosure, the polyester film contains glass spheres having an average particle size of 2-3 microns and a particle distribution of 99.9% below about 8 microns. U.S. Pat. No. 6,544,644 is directed toward abrasion resistant spun articles and discloses threads, fibers, or filaments containing 0.05-20 wt % nanoparticles dispersed in the resin. U.S. Pat. No. 6,838,173 pertains to a polyester fiber and production method of polyester composition. In that disclosure, the polyester fiber comprises silica-based inorganic particles (1-20 wt %) with an average particle diameter of 0.01-10 microns. U.S. Pat. No. 8,691,906 discloses a method for producing monofilament fibers comprising an aliphatic-aromatic polyester, a hydrolysis stabilizer, and spherical particles of oxides of silicon, of aluminum, and/or of titanium having an average particle diameter of not more than 100 nm. U.S. Pat. No. 8,383,716 relates to polyester nanocomposites made of polyester and silica nanoparticles therein, where the surface of the nanoparticles is modified by 3-[(propyleneoxycarbonylamido)propyl]-trialkyloxysilane. Finally, U.S. Pat. No. 8,883,917 discloses nylon polymers having a low coefficient of friction and method for preparation of a polyamide-based composition comprising particulate silica substantially uniformly dispersed into a polyamide matrix.
When a fabric structure is used as paper machine clothing, the components (for example, monofilaments in a woven structure) are generally exposed to harmful, abrasive environments that cause wear and tear to the fabrics. A component demonstrating abrasion resistant properties is therefore needed.